8. Which of the following is the mechanism by which calcium channel blockers relieve angina?

A. Arterial vasodilation from smooth muscle relaxation increasing oxygen supply

B. Decreasing heart rate reducing oxygen demand

C. Decreasing contractility reducing oxygen demand

D. A and B are correct

E. All of the above are correct

There are two types of calcium channel blockers. Dihydropyridine calcium channel blockers (amlodipine, nifedipine) act on peripheral calcium channels to cause smooth muscle relaxation and arterial vasodilation. This increases oxygen supply when the coronary arteries are vasodilated and decreases afterload (blood pressure) and thus LV pressure which reduces oxygen demand. Vasodilation of coronary arteries also reduces vasospasm. Non-dihydropyridine calcium channel blockers (diltiazem, verapamil) act on the myocardium to decrease heart rate and contractility, thus reducing myocardial oxygen demand.